Electricity is an indispensable resource in society. The generation of electricity may take many forms including coal, gas, oil, hydroelectric, and nuclear generation techniques. Since each of the techniques for generating electricity can have a detrimental impact on society, it is often desirable to minimize the amount of electricity or electrical power consumed by various electrical systems. While reducing power consumption is often a goal in designing electrical systems, system designers also must consider the impact that reducing the power consumption will have on the overall system functionality. For example, in the context of lighting systems, power consumption may be reduced by dimming the lights, yet such a practice may yield unacceptably low levels of light especially in incandescent lighting systems. However, certain lighting systems exist that can accommodate lower voltage levels without hindering operation—e.g., florescent lamps and high intensity discharge (HID) lamps.
In general, florescent lights operate by positioning electrodes at opposite ends of a gas tube filled with a relatively low pressure gas vapor, such as mercury or argon vapor. Electrons flow through the gas from one electrode to the other. As the electrons travel from one electrode to the other, the electrons interact with the vapor in the tube to excite the gas vapor. The gas vapor eventually returns to an unexcited state, and in so doing, releases photons that interact with a phosphor coating on the inside of the tube to produce light.
During florescent lamp operation, a high voltage surge is applied to the lamp to establish an arc in the gas vapor. Once the arc is established, the resistance of the gas vapor decreases, and therefore the current through the tube should be regulated to match the decreasing resistance. Such current regulation usually occurs by regulating the voltage across the lamp. Without regulation, the lamp would draw power unceasingly and would rapidly burn out. A ballast provides the starting voltage and may also regulate the subsequent reduction in voltage across the lamp.
The operation of HID lighting is similar to fluorescent lighting. Namely, an arc is established between two electrodes in a gas filled tube that causes a metallic vapor to produce radiant energy. One major difference between the two technologies is that HID lamps can produce visible light without phosphorus. In addition, the electrodes of an HID lamp are only a few inches apart and the gases in the tube are highly pressurized.
Akin to florescent technology, a ballast is required in order to operate the HID lamp and regulate the voltage provided to the lamp once an arc is established. Unlike fluorescent lamps, HID lamps require a warm-up period to achieve full light output, and in some cases the lamps require several minutes before they can be re-ignited after they are shut off. Accordingly, methods and apparatuses for regulating the amount of power consumed by lighting systems are desirable.